1. Field of the Invention
The present invention relates to the use of multiple compressors to provide extra capacity in the heating mode at low ambient temperatures in reversible refrigeration systems (heat pumps). This invention more particularly pertains to utilizing a single or primary compressor above particular temperature set points determined as a function of a percentage of maxium allowable system design mass flow and then multiple compressors simultaneously in parallel to the primary compressor when below the particular temperature set points determined for each additional compressor while on the heating mode of operation such that the heat output remains constant at lower ambient temperatures. In the cooling mode and down to the first temperature set point on heating a primary compressor alternates with any one of a number of the secondary compressors in singular compressor operation to extend the life of the compressors.
2. Description of the Background Art
Presently, most commercially available multiple compressor systems use dual compressors only in the cooling mode where the second compressor is used primarily for extra cooling capacity at high ambient temperatures. These known dual compressor systems are used in the cooling mode only. Such a system requires an oversized condenser and evaporator compared to the primary compressor when in the first stage cooling mode. This is because when both compressors are running in the second stage cooling mode an increased mass flow of refrigerant is created through the entire system. In other words, the entire refrigeration system would have to be sized to accommodate the increased flow of refrigerant due to the existence of multiple compressors running simultaneously in parallel in the cooling mode at high ambient temperatures.
With regard to these known multiple compressor refrigeration systems, these systems are simply oversized, configured at a considerably higher cost and perform with high efficiency only when the primary or first stage compressor is running in the cooling mode. Moreover, the simultaneous use of multiple compressors in the cooling mode will likely reduce the life expectancy of the first stage compressor prior to the typical life expectancy of single compressor systems.
In response to the realized inadequacies of these earlier, multiple, compressor systems, it became clear that there is a need for a multiple compressor system capable of being utilized in both the heating and cooling modes of operation but which is sized for only a single compressor in the cooling mode. This device must provide for an increased mass flow of refrigerant at low outside ambient temperatures by providing multiple compressors such that the heat output remains equal to that of the primary compressor operating solely at higher outside ambient temperatures. However, while in the heating mode at higher ambient temperatures, a single, primary compressor dictates the component sizing of the overall refrigeration system. Moreover, the primary compressor is itself sufficient in the cooling mode. Thus, the device of the present invention may allow alternate use of compressors in the cooling mode to extend the life expectancy of the overall system. In as much as the art consists of various types of multiple compressor refrigeration systems, it can be appreciated that there is a continuing need for and interest in improvements to multiple compressor systems, and in this respect, the present invention addresses these needs and interests.
Therefore, the principal object of this invention is to provide an improvement which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of refrigeration systems.
Another object of this invention is to provide a new and improved multiple compressor system for use in a refrigeration system that has all the advantages and none of the disadvantages of the earlier multiple compressor systems.
Another object of the present invention is to provide a multiple compressor system for maintaining a heat output at lower ambient temperatures.
Still another objective of the present invention is to provide a multiple compressor system compatible with a refrigeration system sized for the mass flow of a single compressor operating in the cooling mode at higher outside ambient temperatures.
Yet another objective of the present invention is to provide a multiple compressor system having a primary compressor operating above particular outside ambient temperature so points in the heating mode that are determined as a function of a percentage of maxium allowable system design mass flow and then having secondary compressors operate parallel to the primary compressor when the outside ambient temperatures fall below each of the particular temperature set points determined for each additional compressor.
Still a further objective of the present invention is to provide a multiple compressor system wherein the refrigeration system is sized for the mass flow of the primary compressor when operating in the cooling mode but the secondary compressors alternate with the primary compressor for singular operation in the cooling mode.
Yet a further objective is to provide in a refrigeration system of the type having a condenser, evaporator, refrigerant and the capabilities of at least heating and cooling modes of operation, a multiple compressor system in parallel operation comprising, in combination, a primary compressor and at least one secondary compressor, the condenser and evaporator sized for the maximum mass flow determined. for the primary compressor operating in the cooling mode, the primary compressor operating by itself when in the heating mode above the first temperature set point; the secondary compressor commencing operation in the heating mode of operation below that first temperature set point and concurrently operating with the primary compressor such that mass flow of the refrigerant through the refrigeration system in the heating mode of operation is no greater than the maximum mass flow determined for the primary compressor operating solely in the cooling mode of operation.
An additional objective is to provide in the method of operation of a refrigeration system of the type having a condenser, evaporator, refrigerant and the capabilities of at least heating and cooling modes of operation, the method comprising the steps of passing the refrigerant from the evaporator of the refrigeration system to a primary compressor in the heating mode of operation for compressing the refrigerant and supplying same to the condenser of the refrigeration system, the primary compressor operating exclusively in the heating mode of operation above a first temperature set points; controlling the exclusive operation of the primary compressor by selecting the temperature set point above which the primary compressor is the sole means for compressing refrigerant; and passing the refrigerant from the evaporator of the refrigeration system to the primary compressor and a secondary compressor while in the heating mode of operation and below the first temperature set point such that the mass flow of the refrigerant through the refrigeration system in the heating mode of operation is no greater than that maximum mass flow determined for the primary compressor operating solely in the cooling mode of operation.
Another objective is to provide in the method of operation of a refrigeration system, the method further comprising of the step of alternating exclusive operation in the cooling mode of operation of at least one of the secondary compressors with the primary compressor.
The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a more comprehensive understanding of the invention may be obtained by referring to the summary of the invention, and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.